The invention relates to a water-conducting household appliance having a rotatable component, which is rotatably mounted on a stationary component of the household appliance by way of a bearing formed from a metallic material. The household appliance also includes a sealing element, by means of which the bearing is sealed off from a liquid chamber of the household appliance, wherein a contact surface of the sealing element is brought into contact with a contact surface of a shaft part which is connected to the moveable component and can be rotated relative to the sealing element, and slides on the contact surface of the shaft part.
Interest presently focuses in particular on a household appliance for the care of items of laundry, in which the laundry drum is rotatably mounted on a wash tub by way of a bearing. The bearing, for instance a ball-bearing, is usually located inside a bearing chamber, which is separated for liquids from the interior of the wash tub with the aid of a sealing element or sealed off from the interior of the wash tub. It is prior art that the bearing chamber is filled with lubricating oil or lubricating grease. The lubricating oil or lubricating grease in this case assumes two different functions, namely on the one hand the function of lubricating the metallic ball bearing and on the other hand also the function of keeping water from the ball bearing. The metallic ball bearing namely represents a component which is sensitive to corrosion. The bearing chamber, as already explained, is separated for liquids from the wash tub, which can be filled with water, by means of the sealing element, but the possibility of individual droplets of water entering the bearing chamber over the entire service life of the household appliance cannot be excluded.
A schematic representation of internal components of a washing machine known from prior art is shown in FIG. 1. A laundry drum 3 is used to receive items of laundry and is rotatably mounted about an axis of rotation 4 running horizontally. The laundry drum 3 is connected to a pulley 6 by way of a shaft 5. While the laundry drum 3 is disposed within a stationary wash tub 7, the pulley 6 is disposed outside of the wash tub 7. The laundry drum 3 here represents a moveable component of the washing machine, and the wash tub 7 represents a stationary component of the washing machine.
The laundry drum 3 is rotatably mounted on the wash tub 7. To this end, a bearing device 8 is provided, which includes a bearing housing 9 and a bearing 10 arranged in the bearing housing 9. The bearing 10 is for instance a ball bearing. An enlarged representation of the bearing device 8 is shown schematically in FIG. 2. The bearing 10 is in a bearing chamber 11, which is filled with lubricating oil 12. The bearing chamber 11 is sealed off from the interior 14 of the wash tub 7 and/or the interior of the laundry drum 3 by means of a sealing element 13. The interior 14 in this case represents a liquid chamber, in which water can be received. The sealing element 13 is provided in the form of a circumferential shaft sealing ring, which is embodied in the shape of an L in the longitudinal section and includes a annular element 15 running radially, from which two lips protrude in the axial direction in the region of the shaft 5, namely on the one hand a first lip 16 in the direction of the interior 14 and also on the other hand a second lip 17 in the direction of the bearing chamber 11. While the first lip 16 rests directly on the shaft 5 and thus prevents the penetration of water into the bearing chamber 11, the second lip 17 rests on a sliding ring and/or sleeve 18 in the radial direction, which is connected to the shaft 5 and is sealed with an O-ring 19 at an end facing the interior 14. The sealing effect of the second lip 17 is enhanced by a circumferential spiral spring 20.
Even with a particularly reliably sealed bearing chamber 11 of this type, it is not possible, throughout the entire service life of the washing machine, to exclude droplets of water being able to reach the bearing chamber 11 by 100%. For the formation of rust on the ball bearing, three conditions must simultaneously be fulfilled: metal (for instance iron), water and oxygen must be present. Rust in this case refers to a complex corrosion product which is produced from iron by oxidation with oxygen in the presence of water. Rust is therefore an oxide of the iron which contains water, namely an agglomeration of iron, oxide and hydroxide ions with water. With respect to the formation of rust, reference is made to FIG. 3, in which a component 1 formed from iron Fe corrodes on account of a droplet of water 2 present. If the iron component 1 comes into contact with water, damp air or another electrolyte, the oxygen dissolved in the water attacks the metal, which is referred to as oxidation. A galvanic cell is formed, so that electrons are removed from the metal and the positively charged ions pass into the solution. Thus the metal corrodes. This is particularly disadvantageous in a washing machine. A thus corroded bearing leads to a marked development of noise in the washing machine, namely in particular during spinning. This frequently results in unnecessary costs, since the entire bearing can only be replaced with a relatively large outlay.